a. Preheat your oven to 350°F (175°C).

a. In a mixing bowl, combine 1 1/2 cups (180g) of flour, 1 tsp of baking powder, and a pinch of salt.

b. Add 2 tsp of vanilla sugar (or 1 tsp of vanilla extract), 1 tbsp of finely grated lemon rind, and 1/4 cup (50g) of granulated sugar to the dry ingredients.

c. Cut in 6 tbsp (85g) of room temperature butter until the mixture resembles coarse crumbs.

d. Stir in 1 beaten egg to form a dough.

e. Press the dough evenly into the bottom of a greased 9-inch (23cm) springform pan, creating a crust.

a. In a separate mixing bowl, whisk together 3 egg yolks and 3/4 cup (150g) of granulated sugar until well combined.

b. Add 2 tsp of vanilla sugar (or 1 tsp of extract) and 6 tbsp (85g) of room temperature butter to the egg mixture and mix until smooth.

c. Stir in 3/4 cup (170ml) of heavy cream and 2 cups (450g) of plain Quark (or Greek yogurt) until fully incorporated.

d. In a small bowl, dissolve 1 1/2 tsp of cornstarch in a little water to create a slurry, then add it to the filling mixture and blend well.

e. In a separate bowl, beat 3 egg whites with a pinch of salt until stiff peaks form. Gently fold the beaten egg whites into the filling mixture until fully combined.

a. Pour the filling over the prepared crust in the springform pan, spreading it evenly.

b. Place the pan in the preheated oven and bake for approximately 45-50 minutes or until the cheesecake is set and the top is lightly browned.

c. Remove the Käsekuchens from the oven and let it cool in the pan on a wire rack.

d. Once cooled, refrigerate the cheesecake for several hours or overnight to allow it to firm up.

a. Carefully remove the cheesecake from the springform pan.

b. Slice the Käsekuchens into portions and serve chilled.